High Refractive Index without Absorption in a Ladder-Type System

A three-level ladder-type system with vacuum-induced coherence and incoherent pumping is studied to obtain a high refractive index without absorption. It is shown that the enhancement of the refractive index without absorption can be accomplished by choosing the proper values of the incoherent pumping, the angle between the two dipole moments, the probe detuning and the relative phase of the two coherent fields.